Bump ministryofjustice/github-actions from 18.3.1 to 18.4.0

Bumps [ministryofjustice/github-actions](https://github.com/ministryofjustice/github-actions) from 18.3.1 to 18.4.0.
- [Release notes](https://github.com/ministryofjustice/github-actions/releases)
- [Commits](ministryofjustice/github-actions@9f2e106...721b0f2)

---
updated-dependencies:
- dependency-name: ministryofjustice/github-actions
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

.github/workflows/images.yml

@@ -147,7 +147,7 @@ jobs:
 
       - name: Set Up Container Structure Test
         id: setup_container_structure_test
-        uses: ministryofjustice/github-actions/setup-container-structure-test@9f2e1064389dae6ca4098470b933da7042675e59 # v18.3.1
+        uses: ministryofjustice/github-actions/setup-container-structure-test@721b0f273fc8356611cb18b3dfc02074d59217da # v18.4.0
 
       - name: Set Up QEMU
         id: setup_qemu